Oxidation of benzene compounds



Patented Jan. '20, 1931 v i UNITED STATES PATENT oFriCa OXIDATION OIBENZENE COMPOUNDS Io Drawing. Application filed August 29, 1929, SerialNo. 389,313, and in Germany September 5, 1928.

The invention relates to the oxidation of benzene compounds and inparticular comprises a process of obtaining valuable oxygenatedcompounds from alkyl benzenes I with a side chain connected to twocarbon atoms of the benzene nucleus, especially benzo polymethylenecompounds by oxidizing them by means of gaseous oxygen or a gascontaining oxygen at elevated temperature in the presence ofan-oxidation catalyst. I

As we have set forth in our copending appl'ication Serial No. 242,284,filed December 23, 1927, those alkylbenzenespossessing two or morecarbon atoms in the side chain can be converted .to oxygenatedcompounds, chiefly alcohols and ketones by reacting upon saidydrocarbons with gaseous oxygen or gases containing oxygen at elevatedtemperature above 50 C. in the presence of an oxidation catalyst.

The present invention represents a further development and in accordancetherewith we have ound that the oxidation process described in theaforesaid patent is not restrict ed to those alkyl benzenes having anopen side chain of two or more carbon atoms but that those benzenecompounds the side chain of which is connected with two carbon atoms ofthe benzene nucleus thus forming asecond ring will be converted tovaluable oxy enated products by treating them in liqui phase withgaseous oxygen or gases containing oxygen at a temperature above 50 C.inthe presence of an oxidation catalyst. In particular benzopolymethylene compounds such as hydrindene, tetrahydronaphthalene andthe substitution products thereof preferably those compounds having afree a-POSltlOIl in the alicyclic ring are readily oxidized to alcoholsand ketones.

The oxidation catalysts employed may be of different kinds. Preferablythe oxides and hydroxides of heavy metals have given excellent resultsand in some cases the corresponding metals are operative. The state ofdivision of the oxidation catalyst is, however, of great importance,since a more finely divided catalyst offering a large surface areaexerts an increased oxidizing action. Inter alia the finely dividedoxides of copper, iron and nickel have proved particularly eflicacious.The oxidation catalysts may be used singlyeor mixed with one another orthey may precipitated upon an inert substance or carrier, such aspumice,'calcium carbonate l5 silica gel. or the like.

- The temperature of the reaction may vary, say, from about C. to theboiling point of the compound to be oxidized; depending in each caseupon the respective oxidation catalyst used. As already stated, a tyical fea-' oxidized and the oxidation catalyst into, for

example, a cylindrical vessel of a small diameter and a considerableheight provided with a device'for admitting in the lower part of thevessel oxygen or gases containing oxygen such as air. The current of airbubbles through the liquid and passes through a condenser, constructedand arranged in such a manner that the water formed during the reactionis continuously separated. When oxidation has proceeded to the desiredextent, the unchanged starting material is'distilled ofl after havingremoved the catalyst, and the remaining oxidation products are isolatedby fractional distil ation in a high vacuum.

The invention is illustrated by the following exampgles, but not limitedthereto. The parts are y weight.

Example 1 An oxidation catalyst is prepared by precipitating a 20percent of copper sulfate con taining aqueous solution by means of anex- 18 cess of a caustic soda solution at room temperature, decanting,filtering, washing and drying the precipitate at about 100 C. 20 partsof this catalyst are added to 2000 parts of tetrahydronaphthalene in ahigh cylindrical iron vessel of a small diameter and air is passedthrough the mixture at about 80 to 90 C. According to the layer ofliquid and the velocity of the current the air leaves the mixture with acontent of oxygen varying between Oand 4 percent. hen about 50 litres ofoxygen are absorbed by every kilogram of tetrahydronaphthalene,absorption comes to a standstill whilst about parts of water distil inthe course of the reaction. By distilling off the unchangedtetrahydronaphthalene a residue remainswhich yields about 600 parts ofoxidation products boiling from 130 to 135 C. under a pressure of 15 mm.and consistin of 80 percent of a-keto tetrahydronaphtha ene and 20percent of a-hydroxy tetrahydronaphthalene, besides some 1.2dihydronaphthalene produced from the hydroxy tetrahydronaphthaleneduring distillation.

' Ewample 2 20 parts of the oxidation catalyst prepared according toExample 1 are added to 1000 parts of ar-ethyl tetrahydronaphthalene(prepared in accordance with U. S. Patent 1,7 66,344 of June 24, 1930 toMichel application Serial No.- 268,363, filed April 7, 1928, by reactingwith ethylene upon tetrahydronaphthalene in the presence of an aluminumhalide) and oxygen is introduced into the mixture for some 56 hours.During this time 50 parts of water are produced. After distilling offthe unchanged tetrahydronaphthalene there are obtained at a pressure of30 mm. 300 parts of liquid oxidation products which consist of percentof a ketone and of 25 percent of the corresponding secondary alcohol andwhich readily dissolve nitrocellulose. A. slight residue is left in thestill. The ketone is believed to be an ar-ethyl oz-kGtOtetrahydronaphthalene. Byv mixing it with semi-carbazide hydrochloridein an aqueous-alcoholic solution it is converted to a semicarbazonerecrystallizable from toluene and melting at 223 C.

E era-m ple 3 20parts of the oxidation catalyst in accordance withExample 1 are added to 2000 parts of ar-chloro tetrahydronaphthaleneboiling from 120 to 130 C. at 15 mm. pressure (prepared by chlorinatingtetrahydronaphthalene at a low temperature 'in the presence of achlorination catalyst such as anhydrous ferric chloride). The mixture istreated at about 100 C. with oxygen for some 25 hours. During this time35 parts of water are produced. After distilling ofi the unchangedchloro tetrahydronaphthalene there are obtained 300 parts of liquidoxidation products boiling at about 160 C. under 20 mm. pressure whichare soluble in concentrated sulfuric acid for about 75 percent. Theyconsist of a mixture of a chlorinated a-keto tetrahydronaphthalene andthe corresponding alcohol and are good solvents for nitro cellulose. Inan aqueous-alcoholic solution the ketone is converted by semicarbazidehydrochloride to a semicarbazone recrystallizable from cyclo-' hexanoland melting at 210 (1, which is insoluble in water and slightly solublein alcohol, benzene and tetrahydronaphthalene.

Example 4 700 parts of tetrahydronaphthalene aredistetrahydronaphthalene containing about 20 percent of a-hydroxvtetrahydronaphthalene.

Emample 5 An oxidation catalyst is prepared by precipitating at roomtemperature, a 10 percent solution of potassium chromium sulfate, bymeans of the calculated amount of aqueous ammonia having a strength of10 to 20 percent, decanting, filtering and drying the precipitate atabout 100 C. 20 parts of the hydrated chromium oxide thus obtained andsifted afterwards are added to 2000 parts of tetrahydronaphthalene; themixture is subjected to a vigourous current of oxygen at to 125 C. in acylindrical iron vessel having a small diameter and a large height forsome 3 to 5 hours. The water produced during this time is allowed tocontinuously distil off. The reaction product filtered from the catalystyields after distilling off the unchanged tetrahydronaphthalene some 600to 700 parts of oxidation products from which a-ketotetrahydronaphthalene (containing a little amount of a-hydroxytetrahydronaphthalene) may be separated by fractional distillation atextremely reduced pressure.

Example 6 A 30 percent caustic soda solution is added to a 10 percent ofmanganese sulfate containing solution until. the liquid shows analkaline reaction. The precipitate is decanted, filtered and dried atabout 100 C. 20 parts of the manganese oxide thus obtained are finelypulverized, mixed with 2000 parts of tetrahydronaphthalene and treatedwith a current of oxygen as shown in Example 5 at a temperature of 85 to130 C. During this time about 70 parts of water are produced and distiloff. After filtering the catalyst 600 to 700 parts of oxidation productare obtained.

I Ewample 7 A 10 percent of nickel sulfate containing solution isprecipitated by means of a 10 percent caustic soda solution at roomtempera 10 turc until the liquid shows an alkaline reaction decanted,filtered and dried at about 100 parts ofthe nickeloxide'thus obtainedare finely pulverized, and added to 2000 parts of tetrahydronaphthalene.The

5 mixture is oxidized in accordance with Example 5. There are obtainedabout 600 parts of oxidation products which yield about 500. parts ofa-keto tetrahydronaphthalene (in addition to some a-hydroxy tetrahydro20 naphthalene) on distillation win a' high vacuum.

If the oxidation temperature rises too high or the distillation of theoxidation products is not carried out under extremely reduced ressure,the a-hydroxy tetrahydronaphthaene present in the mixture readily splitsofi water and is converted to 1.2 dihydronaphthalene. J t We claim:

1. The process which comprises reacting upon an alkyl benzene with aside chain connected with two carbon atoms of thebenzene nucleus, inliquid phase with a gas contain- .ing oxygen at atemperature above C. in

35 the presence of an oxidation catalyst.

ture not below the presence of an inorganic oxidation: catalystcomprising a heavy metal oxide.

' 8..The process which comprises reacting upon tetrahydronaphthalenewith air at a temperature of about '80 to C. in the presenceof finelydivided copper oxide.

9. The process which comprises reacting JOSEPH BINAPEL.

2. The process which comprises reacting upon a benzo polymethylenecompound in liquid phase with a gas containing oxygen at a temperatureabove 50 C. in the presence 40 of an oxidation catalyst. r 4

3. The processjwhich comprisesreacting upon a benzo polymethylenecompound in liquid phase with a gas containing oxygen at a temperatureabove 50 C. in the presence (.5 of an inorganic oxidation catalyst.

' 4. The process which comprises reacting upon a benzo polymethylenecompound in liquid phase with a gas containing oxygen at a temperatureabove 50 C. in the presence 50 of an inorganic oxidation catalystcomprising. a compound of a'he'avy metal.

'upon a benzo polymethylene compound with 5. The process which comprisesreacting upon a benzo liquid phase with a gas containing oxygen 55 at atemperatureabove 50 C. inthe pres ence of an inorganic, oxidationcatalyst comprising a heavy metal oxide.

' 6. The procew which comprises reacting polymethylene 'compound in p iupon a benzo polymethylene compound'in.

liquid phase with a gas containing oxygen at a temperature above. 50 C.in the presence l of finely divided cooper oxide.- 7. The upon tetraydronaphthalene in liquid phase with a gas containlng oxygen at atemperaa process which comprises reacting

